In particular motor vehicles having a diesel engine and an exhaust gas aftertreatment unit which includes a particle filter situated in the exhaust tract of the diesel engine are frequently equipped with a differential pressure sensor which may be used to detect the difference between exhaust gas pressures upstream and downstream from the particle filter in order to deduce the instantaneous loading of the particle filter with soot particles or the optimal time for regenerating the particle filter, by evaluating the detected pressure difference.
All-terrain vehicles in particular must generally have a certain minimum fording capability in order to travel through shallow water, whereby their tailpipe outlet may go under the water surface. To prevent water which penetrates into the tailpipe from flooding parts of the exhaust tract and thus causing damage to the particle filter or other components of the exhaust gas aftertreatment unit, fording-capable motor vehicles are generally designed in such a way that during operation the internal combustion engine cannot stall when traveling through shallow water, and the exhaust gas pressure generated during operation of the internal combustion engine prevents water from reaching the rear muffler.
As the result of continuing efforts in the motor vehicle industry to reduce exhaust gas emissions from and fuel consumption in motor vehicles, it is becoming increasingly common to equip motor vehicles with a hybrid drive, and with a so-called automatic start-stop system which shuts off the internal combustion engine as a function of detected operating parameters such as battery charge state, engine temperature, catalytic converter temperature, accelerator or brake pedal position, and gear selection, for example, in different operating states and restarts the engine, for example when the vehicle is at a standstill.
When the all-terrain or fording-capable motor vehicles are micro, mild, or full hybrid vehicles having an automatic start-stop system, situations may arise in the operation of these vehicles in which the automatic start-stop system shuts off the internal combustion engine when the vehicle is traveling through shallow water, for example when the vehicle is stopped when crossing a body of water. If the outlet of the tailpipe is completely or partially below the water surface at that time, this may result in parts of the exhaust tract being flooded with water due to the lack of exhaust gas pressure.